Derek Crilly's 35th-minute goal was the decisive score as Louth edged out Westmeath in Mullingar.
John Heslin's free nudged the home team in front in the third minute. Seven minutes later, James Dolan (Westmeath) and Conor Martin (Louth) picked up black cards after a relatively innocuous tussle.
The Louth forwards found it a little easier than their hosts to pick off scores and they were level when Crilly found the net approaching the interval, after David Bryan had done well to keep out initial efforts from both Conal McKeever and Crilly.
Louth led by 1-5 to 0-5 at the interval.
Substitute James Califf was an influential figure for the visitors and his point in the 42nd minute - moments after Anthony Williams had slapped the ball off the crossbar with the net gaping - put the Wee County 1-8 to 0-6 clear.
Louth still held a four-point lead with four minutes of normal time remaining.
Tom Cribbin's hosts pressed hard in the closing stages and were rewarded with three unanswered points, two of them from impressive sub Alex Gardiner.
However, Westmeath wing-back Shane Corcoran was wide when a goal beckoned, and Colin Kelly's troops held on.
Only two 'marks' were awarded throughout the entire game.
Scorers - Louth: D Crilly 1-1, J Califf (1f), R Holcroft (1f) 0-2 each, P Rath, T Durnin, D Byrne, P Smith 0-1 each. Westmeath: J Heslin 0-5 (5f), A Gardiner 0-2, P Holloway, K Martin, C McCormack, S Dempsey 0-1 each.
Louth - C Lynch; P Rath, P Reilly, K Carr; D Maguire, D McMahon, A Williams; C Martin, T Durnin; D Byrne, P Smith, B Duffy; C McKeever, D Crilly, R Holcroft. Subs: J Califf for Martin (BC, 10), D Marks for Maguire (BC, 48), R Nally for McKeever (60), R Moore for Crilly (60), R Carroll for Holcroft (60), J Bingham for McMahon (64), D Finn for Marks (BC, 66).
Westmeath - D Bryan; J Gonoud, K Maguire, K Daly; S Corcoran, A Stone, J Dolan; P Holloway, J Heslin; C Boyle, K Martin, K Reilly; C McCormack, S Dempsey, F Boyle. Subs: D Lynch for Dolan (BC, 10), A Gaughan for Stone (h-t), D McNicholas for C Boyle (54), J Marshment for F Boyle (56), D Glennon for Dempsey (58), A Gardiner for McCormack (58), N Mulligan for Corcoran (68), T McDaniel for Martin (70 +2).
Ref - D Hickey (Carlow).